Overview: Children with regressive autism have larger brains than children with early-onset autism or non-autistic peers report researchers at the University of California, Davis School of Medicine.

Background: In a report published in the Proceedings of the National Academy of Sciences on November 28, the researchers examine the association between total brain volume and the age of symptom onset in a large group of 2- to 4-year-old boys and girls with autism spectrum disorder (ASD).

What’s new: According to the study, the boys with regressive autism have abnormal brain enlargement, while brain measurements in boys with early-onset autism are similar to those of controls. The head circumferences of boys with regressive autism are normal at birth but begin to differ from the other groups at approximately 4 to 6 months of age.

Why it’s important: These findings support the growing consensus that varying conditions within the autism spectrum have different underlying pathologies. However, the brain size disparity appears to be gender specific; no differences were reported in brain size of female patients, no matter their diagnosis.

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